The present invention generally relates to an automotive differential. More specifically, the present invention relates to an automotive differential which can be selectively engaged with the drive shaft of the vehicle.
In an automotive vehicle, a differential gear assembly is used to transfer power from a rotating driveshaft to the axles and wheels of the vehicle. The rotating driveshaft of the vehicle engages a ring gear which is mounted onto a differential housing. The end of the driveshaft and the ring gear are adapted to transfer rotation from the drive shaft to the differential housing such that the differential housing rotates transverse to the driveshaft.
Typically, the drive shaft is always engaged with the ring gear of the differential, however, at times it may be desirable to disengage the differential from the drive shaft. One way of doing this is to provide a clutch pack within the differential assembly which is mounted between and interconnects the differential to the drive shaft of the vehicle. When an axial force is placed upon the clutch pack, rotational motion will be transferred from the drive shaft, through the clutch pack, and to the differential.
One way of applying an axial force onto a clutch pack of this type is with a ball ramp. A ball ramp is comprised of a pair of plates having opposing channels formed therein. Within the channels are balls. The height of the balls is such that the plates are not allowed to touch. The channels are ramped such that when one plate rotates relative to the other, the balls will roll up the ramped channels and force the plates apart, thereby producing an axial force.
Over time, the channels within the plates will wear, which means less axial movement of the plates occurs as the ball bearings roll up the ramped surfaces. This reduces the amount of axial force produced by the ball ramp, and affects the performance of the clutch. The only way to repair this condition is to reposition or replace the ball ramp. Further, a ball ramp will only move a limited distance away from the clutch pack. Therefore, the clutch pack cannot be relieved further to allow cooling.
Therefore, there is a need for a differential having a clutch pack for selectively engaging the drive shaft of the vehicle and the differential having a device that applies an axial force to the clutch pack and can be tuned to accommodate for wear of the clutch pack and wear within the device, as well as allowing the device to be backed away from the clutch pack to allow the clutch pack to cool.